Belt-driven bench grinder powered by built-in small series motor



Filed Jan. 21, 1963 WITNESS R. HAPPE 3,142,945 BELT-DRIVEN BENCH GRINDER POWERED BY BUILT-IN SMALL SERIES MOTOR 3 Sheets-Sheet 1 Fig.l

INVENT'OR. Reynold Happe A ORNEY 4, 1964 R. HAPPE BELT-DRIVEN BENCH GRINDER POWERED BY BUILT-IN SMALL SERIES MOTOR 3 Sheets-Sheet 2 Filed Jan. 21 1963 nnnnnn lull) INVENTOR. Reynold Happe Fig.2

WITNESS //W% ATUZRNE Y Aug. 4, 1964 R. HAPPE 3,142,945

BELT-DRIVEN BENCH GRINDER POWERED BY BUILT-IN SMALL SERIES MOTOR Filed Jan. 21, 1963 v 3 Sheets-Sheet 3 INVENTOR.

Reynold Happe wmvsss AT QR MEY 3,142,945 BELT-DRIVEN BENCH GRINDER POWERED BY BUILT-IN SMALL SERIES MOTOR Reynold Happe, Greenville, S.C., assignor, by mesne assignments, to The Singer Company, New York, N.Y.,

a corporation of New Jersey Filed Jan. 21, 1963, Ser. No. 252,800 Claims. (Cl. 51-166) This invention relates to small low-cost bench grinders powered by small, high-speed electric motors of the series commutator type and more especially to an arrangement of parts which facilitates low-cost assembly consistent with high torque output available at the grinding wheel.

It has been common practice in the art of bench grinders to use two-pole induction motors with doubleended shafts for directly driving the grinding wheels. These motors have invariably been of the induction type and physically large, approaching or even exceeding in diameter the size of the wheels they drive and they have been expensive per unit power output due to the inherent low speed limitation imposed by the frequency and pole number.

This problem has been overcome by this invention wherein a high-speed series commutator type motor is coupled to the Wheel shaft by means of a timing-belt speed reducer. The much higher motor speed thus obtainable reduces the amount of active material in the motor and thus its cost per unit power output. The cost is further reduced by using a skeleton type motor contained in suitable recesses formed in the halves of a twopart grinder housing split preferably along a vertical plane containing the grinding wheel shaft axis.

It is an object of this invention to provide a small-size low-cost bench grinder powered by a built-in high-speed series commutator motor through a timing-belt speed-reduction drive.

It is a further object of this invention to provide a simple assembly for a self-powered bench grinder having an electric driving motor on one axis, a grinding wheel shaft on another axis, and a non-lubricated, non-slip power transmission therebetween, all supported by a twopart housing split along a vertical plane containing both said axes.

It is still a further object of this invention to provide a bench grinder having a center of gravity located substantially below the grinding wheel axis.

It is a further object of this invention to provide a bench grinder having a driving motor whose outside diameter is less than half the diameter of the grinding wheels.

With the above and other objects in view, as will here inafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

In the drawings,

FIG. 1 is a longitudinal elevational view, partly in section, of one of the housing sections of a bench grinder embodying the invention.

FIG. 2 is a vertical sectional view taken substantially on the line 2-2 of FIG. 1.

FIG. 3 is a perspective view showing the split housing sections in diassembled condition of a bench grinder embodying the invention.

Referring now to FIG. 1, there is shown a base housing section 10, which is basically a cast shell having thin Wall sections 11 for defining separate compartments in which are received various components to be described. The

United States Patent O housing 10 is also formed with bosses 12-12 which provide open seats for receiving self-aligning bearings 13-13 in which is journaled a shaft 14 to the ends of which are secured grinding wheels 15-15. The bearings 13-13 are secured in their seats by means of cover straps 16-16 secured to the bosses 12-12 by screws 17-17. End thrust on shaft 14 in one direction is taken by a washer 18 held captive between one bearing 13 and a split ring 19. In the other direction end thrust is taken by a washer 20 held captive between the other bearing 13 and the hub of a toothed pulley 21 secured to the shaft 14 by pin 22.

A motor, indicated generally at 23 of the series commutator type, has an armature shaft 24 journaled in bearings 25-25 held in open seats in bosses 26-26 by cover straps 27-27 secured to the bosses 26-26 by screws 28-28. The shaft 24 carries a wound rotor core or armature 29 and a commutator 30. Brushes 31-31 held within insulated boxes 32-32 secured within recesses 33-33 by means of screws 34-34, bear against the commutator 30. A wound stator core 35 is held in a seat 36 formed in a boss 37 by a cover strap 38 secured to said boss by screws 39-39. To prevent rotation of the stator core 35 the seat 36 is formed with a convex portion 40 which keys with a concave portion 41v formed on the periphery of the stator core 35 as clearly shown in FIG. 2.

It will be seen that the motor 23 has no separate housing of its own but relies on wall sections 42 formed in the base section 10 and on mating wall sections 43 formed in a cover section 44 of the grinder housing to perform this function. This structure is not only less expensive but provides better heat sinking for the motor than would be the case if a conventional separate motor housing were used.

A toothed pulley 45 secured to the motor armature shaft 24 by means of set-screw 46 is drivingly connected to the pulley 21 and thus to the grinding-wheel shaft 14 by a cog-belt 47. The relative pulley diameters are such as to provide a speed reduction of approximately 4: 1. Thus the motor 23 may be, designed for a full-load speed of 18,000 rpm. to yield approximately 4500 r.p.m. at the grinding-wheel shaft 14. The very high motor speeds made possible by this arrangement yield a motor of very small dimensions consistent with adequate torque and speed at the grinding-wheel shaft compared with the direct-drive motors of the grinders of the prior art. The motor is thus .no longer the factor governing the size of the grinder and according to this invention becomes an item of minor cost. As a matter of fact, the outside diameter of the stator core 35 of the motor 23 is less than half the diameter of the grinding-wheels 15 which it drives.

The use of the positive timing-belt drive eliminates the lubrication which would be necessary if gears were used .and further simplifies the assembly because no seals are required to confine the lubricant Within a gearing housing.

The location of the motor 23 below the shaft 41 results in a low center of gravity for the grinder which promotes stability against tipping and allows the device to be used for light work without securement to a bench if desired, although in its preferred form it is secured to a bench.

Referring to FIG. 3, it will be seen that, with the cover section 44 removed, the base section 10 contains all the essential parts in secured position to form an operative device which facilitates the visual inspection and testing under running conditions. This is of great practical importance where, as here, high production rates are involved in manufacturing the grinder at low cost.

It will also be observed from this construction that, with the cover 44 removed, it is an easy matter to remove the grinding-wheel shaft 14 and its bearings 13-13 from the bearing seats in bosses 12-12 to facilitate removal of the cog-belt 47.

The cover section 44 is essentially a cast shell having thin peripheral wall sections 48 which, when the cover section is assembled to the base section 10, match with the wall sections 11 to form a closed housing except where openings 4949 are purposely provided to form inlet and outlet air vents for circulation of cooling air provided by a fan 50 mounted on the armature shaft 24.

Locating pin 51 formed on the base section match with apertures 52 in the cover section 44 to assist in the proper alignment of the sections which are secured together by means of recessed bolts 53 which pass through the base section 10 and are tapped into the cover section 44 as seen best in FIG. 2.

End guards 5454 are removably secured to the housing sections 10 and 44 to give access for changing the grinding wheels -15. A tool rest 55 is secured to each of the end guards by a bolt 56 and slot 57 arrangement to provide adjustability. Eye-shields 5858, made preferably of transparent plastic material, are adjustably secured to the top of the cover section 44 by means of knurled thumb-screws 59-59.

A slide switch 60 is secured in the top wall of the cover 44 and connects to conductors 61 and 62 to control the supply of power from the line cable 63 to the motor 23. The cable 63 enters the base section 10 through a regular strain-relief bushing. 64-.

From the above it will be perceived that there has been provided according to this invention a bench grinder having a built-in high-speed series commutator motor driving the grinding-wheel shaft through a timing-belt providing a non-lubricated speed reduction power transmission which permits the use of a small, low-cost motor and results in an assembly which is easy to make and test.

Having thus set forth the nature of the invention, what is claimed herein is:

1. A bench grinder comprising a housing split substan tially along a single vertical plane to form, a rear base section and a front removable cover section, anelectric motor secured to said base section and. having an output shaft, a grinding wheel shaft journaled in bearings secured to said base section independently of said cover section and extending with at least one of its ends exterior to said housing, and driving connections between said motor output shaft and said grinding-wheel shaft interiorly of said housing for drivingsaid grinding-wheel shaft at an angular speed less than that of said motor output shaft, the axes of the shafts being located substantially in the plane of the housing-split with the motor located entirely at one side of the grinding-Wheel shaft.

2. A bench grinder comprising a housing split along a generally vertical plane to form a rear base section and a front removable cover section, a series commutator elec tric motor secured to said base section and having an output shaft, a grinding-wheel shaft journaled in bearings secured to said base section independently of said cover section and extending with bothends exterior to said housing, and a cog-belt drivingly connecting said motor output shaft with said grinding-wheel shaft interiorly of said housing for speed-reducing power transmission, the

axes of the said shafts being located substantially in the plane of the housing-split with the motor located below the grinding-wheel shaft.

3. A bench grinder comprising a vertically split housing forming a rear base section and a front cover section, open bearing seats formed in said base section, bearings received in said seats, a grinding-wheel shaft journaled in a first spaced pair of said bearings, a series commutator motor located within said housing, an armature shaft for said motor journaled in a second spaced pair of said bearings, belt means connecting said armature shaft to said grinding-wheel shaft for transmitting power at reduced rotational speed, and means independently of said cover section for securing said bearings in-said open seats whereby the grinder may be operated with the cover section removed to facilitate inspection during assembly.

4. A bench grinder comprising a vertically split housing forming a rear base section and a front removable cover section, recessed portions formed in said base section, bearings received in some of said recessed portions, brushes and a stator core received in others of said recessed portions, an armature, a shaft mounting said armature and journaled in a first pair of said hearings to form with said brushes and said stator core a series commutator motor, a grinding-wheel shaft journaled in a second pair of said bearings, toothed pulleys mounted for rotation with said motor armature shaft and said grindingwheel shaft, and a cog-belt drivingly connecting said pulleys for transmitting power to said grinding-wheel shaft at reduced angular speed.

5. A bench grinder comprising a vertically split housing forming a rear base section and a front removable cover. section, open bearing seats formed in said base section, bearings received in said seats, a grinding-wheel shaft journaled in a first spaced pair of said bearings, a series commutator electric motor located within said housing, an armature shaft for said motor journaled in a second spaced pair of said bearings, endless belt. means connecting said armature shaft to said grinding-wheel shaft for transmitting power at reduced rotational speed, and means independently of said cover section for securing said bearings in said open seats, said cover section, when removed, providing access for easyremoval of the grinding-wheel shaft and its bearings from said bearing seats to facilitate belt renowal.

References Cited in the file of this patent UNITED STATES PATENTS 1,911,857 Stumpf May 30, 1933 1,923,760 Smith Aug. 22, 1933 1,927,655 Belden et al. Sept. 19, 1933 2,003,495 Ritz June 4, 1935 2,020,547 Haas Nov. 12, 1935 2,288,579 Anesi June 30, 1942 2,566,809 Risley et al'. Sept. 4, 1951 2,948,088 Jepson Aug. 9, 1960 FOREIGN PATENTS 752,456 France July 17, 1933 

1. A BENCH GRINDER COMPRISING A HOUSING SPLIT SUBSTAN TIALLY ALONG A SINGLE VERTICAL PLANE TO FORM A REAR BASE SECTION AND A FRONT REMOVABLE COVER SECTION, AN ELECTRIC MOTOR SECURED TO SAID BASE SECTION AND HAVING AN OUTPUT SHAFT, A GRINDING WHEEL SHAFT JOURNALED IN BEARINGS SECURED TO SAID BASE SECTION INDEPENDENTLY OF SAID COVER SECTION AND EXTENDING WITH AT LEAST ONE OF ITS ENDS EXTERIOR TO SAID HOUSING, AND DRIVING CONNECTIONS BETWEEN SAID MOTOR OUTPUT SHAFT AND SAID GRINDING-WHEEL SHAFT INTERIORLY OF SAID HOUSING FOR DRIVING SAID GRINDING-WHEEL SHAFT AT AN ANGULAR SPEED LESS THAN THAT OF SAID MOTOR OUTPUT SHAFT, THE AXES OF THE SHAFTS BEING LOCATED SUBSTANTIALLY IN THE PLANE OF THE HOUSING-SPLIT WITH THE MOTOR LOCATED ENTIRELY AT ONE SIDE OF THE GRINDING-WHEEL SHAFT. 